First principles study of a new half-metallic ferrimagnets Mn₂-based full Heusler compounds: Mn₂ZrSi and Mn₂ZrGe

Half-metallic properties of new predicted Mn₂-based full Heusler alloys Mn₂ZrSi and Mn₂ZrGe have been studied by first-principles full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method based on density functional theory (DFT). Our investigation is focused on the structural, elastic, electronic and magnetic properties of these compounds. The AlCu₂Mn-type structure is found to be energetically more favorable than the CuHg₂Ti-type structure for both compounds and are half-metallic ferrimagnets (HMFIs) with total magnetic moments of 2.000µ_B per formula unit, well consistent with Slater–Pauling rule (M_tot=(24–Z_tot)µ_B). Calculations show that both the alloys have an indirect band gaps, in the majority-spin channel, with values of 0.505 eV and 0.278 eV for Mn₂ZrSi and Mn₂ZrGe, respectively. It was found that Mn₂ZrSi and Mn₂ZrGe preserved their half-metallicity for lattice constants range of 5.85–6.38 Å and 6.05–6.38 Å, respectively, and kept a 100% of spin polarization at the Fermi level. Moreover, the calculated formation energies and elastic constants confirm that these compounds are stable chemically and mechanically, and the good crystallographic compatibility with the lattice of semiconductors used industrially makes them promising magnetic materials in spintronic applications. - Highlights: • For Mn₂ZrZ (Z=Si, Ge) the AlCu₂Mn-type structure is more favorable than the CuHg₂Ti-type. • The calculated elastic constants confirm their mechanical stability. • Their negative estimated formation energies means they can be synthesized. • Their lattice constants match well with those of many semiconductor substrates. • They are predicted to be true half-metallic ferrimagnets. • The band gaps of Mn₂ZrSi~0.51 eV and Mn₂ZrGe~0.28 eV are indirect along, the Γ–X